Surface treatment of plastics

An important and relevant difference between metals and plastics is their surface energy. Polymers have inherently lower surface energy than metals (assuming they are contamination-free), and tend to form intrinsically poor adhesion bonds without some type of treatment. Adhesion is the mechanical resistance to separation of a bonded system and involves the outer surface of a material. Treatment only 

This section describes the significant techniques available for the treatment of plastic surfaces to enhance adhesion (Fig. 5.2). Not all methods have wide commercial application. Some of the techniques are limited in the scope of their use. For example, chemical treatment (acid-induced oxidation) is the most frequently used method to impart adherability to plastic surfaces. Plasma treatment is limited to smaller components and parts. Flame and corona treatments are effective for continuous films (often called webs) and thin sheets of plastic, usually operated at high speed. 

---

Surface treatment of plastic containers is sometimes used to improve barrier properties, or to enhance printability or label adhesion. 

B. Rotrekl, K. Hudecek, J. Komarek, and J. Stanek, Surface Treatment of Plastics, Khimiya... 

Covalent chemical bonds can form across the interface and are Ukely to occur in cross-Unked adhesives and thermoset coatings. This type of bond is usually the strongest and most durable. However, they require that mutually reactive chemical groups should exist. Some surfaces, such as previously coated surfaces, wood, composites, and some plastics, contain various functional groups that under appropriate conditions can produce chemical bonds with the adhesive material. There are ways to intentionally generate these conditions, such as by surface treatment of plastics with techniques like corona or flame treatment. 

Figure C.7 Basic arrangement for corona surface treatment of plastic film. (Courtesy Lepel High Frequency Laboratories)...

Figure 26.16 Schematic of corona surface treatment of plastic film.

Standard relating to the surface treatment of plastics in preparation for adhesive bonding ... 

Automotive and industrial coatings and surface treatment of plastics... 

This theory proposes that adhesion results from molecular contact between two materials and the surface forces that develop. The first step in bond formation is to develop interfacial forces between the adhesive and the substrates. The process of estabtishing continuous contact between the adhesive and the adherend is called wetting. For an adhesive to wet a soUd surface, the adhesive should have a lower surface tension than the critical surface tension of the solid. This is precisely the reason for surface treatment of plastics, which increases their surface energy and polarity. 

Corrosion. Ammonium bifluoride dissolves in aqueous solutions to yield the acidic bifluoride ion the pH of a 5% solution is 3.5. In most cases, NH4HF2 solutions react readily with surface oxide coatings on metals thus NH4HF2 is used in pickling solutions (see Metal surface treatments). Many plastics, such as polyethylene, polypropylene, unplasticized PVC, and carbon brick, are resistant to attack by ammonium bifluoride. 

Inorganic waste with metals from metal treatment and the coating of metals non-ferrous hydro-metallurgy Wastes from shaping and surface treatment of metals and plastics Oil wastes (except edible oils, 0500 and 1200)... 

Plasma surface treatment of many polymers, including fabrics, plastics, and composites, often occurs. The production of ultra-thin films via plasma deposition is important in microelectronics, biomaterials, corrosion protection, permeation control, and for adhesion control. Plasma coatings are often on the order of 1 100 nm thick. 

Plasticizer containment still remains a major problem, particularly for periods of extended use. For instance, most plastic floor tiles become brittle with extended use, mainly due to the leaching out of the plasticizer. This problem has been solved, to some extent, through many routes, including surface treatment of polymer products and the use of branched polymers which are more flexible than linear polymers. 

Presently DOE is funding Air Products Chemical Company for the development of a fluorine surface treatment of tire rubber (crumb rubber) to modify its adhesion properties. This modified rubber could be used in making polymers such as polyurethane and epoxies. The tire rubber might also be used in certain plastics such as polystyrene and PVC, and in rubber products (68). 

D. Brewis (ed.), Surface Analysis and Pre-treatment of Plastics Metals , Applied Science Publishers, London, 1982. 

While the binding of fibronectin appears to be a critical feature in the response of cells to many man-made materials, recent studies have shown that treatment of surfaces with other extracellular matrix components, such as laminin and type IV collagen (60), can greatly alter the biological properties of plastics. Treatment of plastic with a biomatrix derived from a basement membrane tumor can alter the morphology and differentiated state of several cell types (60). Hence, the biological properties of polymeric materials are dependent on the type of extracellular atrix molecule absorbed more than the chemical nature of the polymer itself. 

In the treatment of plastics, the free radicals generated in the reaction chemically modify (ionize) the surface of the TPO thus allowing the color coat to attach itself to the polar TPO surface. The rest of the process is the same as in the Baseline above. QC method TPO surface 1/ FTIR 2/ surface tension Painted part 1/ cross-hatch adhesion 2/other tests. 

---